1. Field of the Invention
The present invention relates to an electric motor for a hybrid vehicle.
2. Background Art
Conventionally, an electric motor for a hybrid vehicle is known which has a rotor disposed and coupled between an internal combustion engine and a transmission, the rotor being coupled to the crank shaft of the internal combustion engine and via a drive plate to the transmission (For example, see Japanese Patent Application Unexamined Publication No. 11-332010 (FIG. 4)).
In this electric motor for a hybrid vehicle, a coupling shaft or the like, for example, is provided that is pressed into the rotor, and one end of the shaft is coupled through bolt fastening or the like to the crank shaft of the internal combustion engine and the other end is coupled through bolt fastening or the like to the drive plate. The inner diameter of the rotor is set so as to have a predetermined interference relative to the outer diameter of the shaft, and the shaft is pressed into the rotor and is fixed in a tight fit state such that the rotor is sandwiched between the internal combustion engine and the transmission and is coupled therewith.
In the above-mentioned example of a conventional electric motor for a hybrid vehicle, because the rotor is fixed only through tight fitting of the coupling shaft pressed into the rotor, a high dimensional accuracy is needed for the inner diameter of the rotor and the outer diameter of the coupling shaft so as to secure a predetermined interference, thereby giving rise to a problem that the machining cost for producing the rotor and the shaft is increased.
Furthermore, because the rotor is positioned only through tight fitting of the coupling shaft pressed into the rotor, if the positional accuracy of the outer diameter of the rotor is deteriorated during, for example, pressing the coupling shaft or the like into the rotor, in an electric motor equipped with a stator opposed to the outer circumference of the rotor, the dimension accuracy of the gap between the rotor and the stator may be disadvantageously deteriorated.